This section introduces aspects that may help facilitate a better understanding of the disclosure. Accordingly, these statements are to be read in this light and are not to be understood as admissions about what is or is not prior art.
A typical approach to power generation includes use of a wound rotor synchronous machine (WRSM) which can be used for voltage regulation. The same machine may be used as a motor, containing increased flexibility associated to a secondary winding which may be used to regulate output torque. Another type of machine is a permanent magnet synchronous machine (PMSM), which typically offers lower loss and higher power densities.
Referring to FIG. 1, a cross-sectional schematic of an example topology for a hybrid machine is shown. The hybrid machine 1 includes a stator assembly 2 and a rotor assembly 3. The stator assembly 2 includes a stator backiron 4 while the rotor assembly 3 includes a rotor backiron 5. The stator assembly 2 further includes a winding 6, configured to provide a magnetomotive force applicable on the rotor assembly 3. The rotor assembly 3 includes a winding 7 and one or more permanent magnets 8 which together generate a magnetomotive force applicable on the stator assembly 3 which together with the magnetomotive force generated by the stator assembly cause rotation of the rotor assembly 3. The stator assembly 2 and the rotor assembly 3 are radially separated by an air gap 12. The flux produced from the rotor assembly 3 may be approximately modeled using a series circuit configuration depicted in FIG. 1 in a cutout spanning the rotor assembly 3 and the stator assembly 2. Based on the model, a combination of two sources identified as Ffd and Fpm, referring to field windings and permanent magnet magnetomotive force, coupled to each other in series, are connected to a further two reluctances pm and g, referring to the permanent magnet and air gap, connected to the two supplies also in series. The magnetomotive force sources in the magnetic circuit, dissipated across the reluctances, produce a flux in the air-gap (Φg), similar to current in an electric circuit comprised of electromotive force sources (i.e. voltage) and resistances. The series combination is terminated at each end at a ground, representing the stator backiron 4 and the rotor backiron 5.
Placement of magnets and field windings within the rotor is a significant factor in the performance metrics of the hybrid machine, one of which is the torque producing capability relative to the machine size or mass and for a given loss. While beneficial when compared to the mass vs. loss characteristics of the WRSM, there are several limitations inherent in the topology shown in FIG. 1.
Given prior machine configurations, the torques, powers, regulation capability, and the achievable torque density associated therewith, there is unmet need for developing machines with improved torque density, power regulation capability, and lower mass for a given power loss compared to machines of prior art.